用了四个小时把Mysql数据库的最后一个外卖项目写完了，总结了一本书的基本知识，学会了很多新的东西。
SELECT title FROM goods LIMIT 1;
SELECT title FROM goods WHERE goodsld=(SELECT MAX(qty) FROM orderdetails);
SELECT title FROM goods WHERE goodsld IN (SELECT goodsld FROM goods WHERE disount<1);
SELECT * from orders WHERE custid=(SELECT custid from customers WHERE custname=123456 AND loginpwd=\'asdfgh\');
SELECT a.custname,a.custaddress,a.invoicecontent,b.unitprice,b.qty,d.catename FROM orders a, orderdetails b,goods c,category d
WHERE a.custid=b.orderid AND b.goodsid=c.goodsld AND c.cateld=d.cateid
AND custaddress=\'北京市和平路\';